Electrical control device



Jan. 19, 1937. Q w HN ET AL 2,068,494

ELECTRICAL CONTROL DEVICE Filed Nov. 2, 1931 mgg'l w. 3

Patented Jan. 19, 1937 UNITED STATES PATENT OFFICE 2,068,494 ELECTRICAL CONTROL DEVICE ware Application November 2, 1931, Serial No. 572,586

Claims. (01. 175- 335) This invention relates to electrical control devices and is particularly applicable to starting devices for electric motors.

The copending application of William C. Stevens and George J. Meuer, Serial No. 309,537, filed October 1, 1928, discloses a push button operated starting device for electric motors inciuding a pair of contact elements, one 'of which is normally open and is operable to control line connections for the motor, and the other of which is normally closed and is operable to control a starting resistance in the motor circuit. The contact elements are provided with an operating mechanism including start and stop push buttons and upon depression of the former push button both of said contact elements are moved out of normal position with a snap action to establish line connections for the motor and to include the starting resistance in the motor circuit. Immediately upon release of the start push button the resistance controlling contact element returns to normal position to shunt the starting resistance and the other contact element is heldin closed position to maintain line connections for the motor by a latching mechanism which is releasable by the stop push button.

The present invention relates to motor starters of the aforesaid character, and has among its objects to provide automatic means which acts upon momentary depression of the start pushbutton to delay return of the resistance controlling element to normal position for an interval which is sufiicient to prevent excessive current in the motor circuit upon exclusion of the starting resistance.

Another object is to provide a starting device for alternating current motors having improved electromagnetic means associated therewith for automatically timing interruption of starting connections and establishment of rurming connections in accordance with predetermined current conditions in the motor circuit.

Another object is to provide an improved electromagnetic restraining device which is adapted for use in connection with alternating current motor starters and control devices of other types and which is readily adjustable to vary the restraining effect thereof. I

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will now be described, it being understood that various modifications may be made in the embodiment illustrated and that certain features of the invention are capable of use in connection with control devices of various types other than that shown in the drawing.

In the drawing,

Figure l isa front elevational view of a motor starter embodying the invention.

Fig. 2 is a side elevational view of the starter shown in Fig. 1, together with a sectional View of an enclosing casing therefor.

Fig. 3 is a sectional view taken substantially on line 3-3 of Fig. 1.

Fig. 4 is an enlarged sectional view of an electromagnetic restraining device shown in Figs. 1, 2 and 3.

Figs. 5 and 6 are end views of the core member,

of the electromagnetic restraining device shown in Fig. 4, illustrating such core member in different positons with respect to its cooperating armature member, and

Fig. '7 is a diagrammatic view illustrating the circuit connections for the starter shown in Fig. 1.

The starting device illustrated is provided with a switch mechanism of the character disclosed in the aforementioned copending application of William C. Stevens and George J. Meuer. Such mechanism includes a pair of U-shaped contact levers l and 2 arranged in opposed relation and having their adjacent ends pivotally mounted upon bearing projections 3 and 4 formedupon a-U-shaped bracket 5 fixed to an insulating base 6. Each of the contact levers i and 2 has an insulated bridging contact mounted upon the free end thereof, the bridging contact 1 associated with lever I being adapted to cooperate with a pair of stationary contact devices 8--8 and the bridging contact 9 associated with lever 2 being adapted to cooperate with a pair of stationary contact devices Ill-40. As shown in Fig. '1, the two pairs of contact devices 8-8 and l0-lll are mounted upon opposite ends of insulating base 5. Each of the contact devices 8-8 is provided with a contact finger 8 to be engaged by bridging contact I when lever i occupies the position shown in Fig. 2, and each of the contact devices Ill-l0 is provided we a contact finger Hi to be engaged by bridging contact 9 when lever 2 occupies the position shown in Fig. 3.

The operating mechanism for contact levers l and 2 includes a tension spring I2 which isconnected at opposite ends to the free ends of contact levers I and 2 by insulating links I3. As is apparent from Fig. 3, movement of the axis of spring l2 in opposite directions across a plane joining bearing projections 3 and 4 provides for snap movement of contact levers I and 2 in opposite directions between the positions illustrated in Figs. 2 and 3. Spring l2 passes through an opening in a reciprocable operating member I4 having a push button I5 fixed to the outer end thereof. Operating member I4 is supported adjacent its inner end within an opening in bracket 5 and is supported adjacent its outer end within an opening in a frame I6 fixed to said bracket. A spring I1 biases operating member I4 outwardly towards the position shown in Fig. 2. Said spring is held under compression between a washer I8 mounted upon said member and a plate I9 fixed to the rear face of base 6 by screws I3 which also serve to secure bracket 5 to said base.

Contact lever 2 has a latch 20 associated therewith for locking the same against movement out of the position shown in Fig. 3. Latch 20 is pivotally mounted upon a pin 2I carried within a recess in the outer face of frame I6 and the same is provided with a shoulder 22 for engaging a projection 23 on contact lever 2. Latch 20 is also provided with an inclined cam surface 24 to be engaged by a reciprocable tripping member 25 having its inner end supported within an opening 25 in base 6 and having its outer end provided with a push button 21 which is supported within an opening in frame I6. Tripping member 25 is formed to provide a face 25 for engaging the cam surface 24 on latch 20 and said tripping member is connected to said latch by a spring 28. Spring 28 serves to bias tripping member 25 outwardly towards the position shown in Fig. 3 and also serves to bias latch 20 upwardly for engagement with the projection 23 on contact lever 2. As is apparent, depression of push button 21 causes the face 25 of tripping member 25 to engage the cam surface 24 on latch 2|] to move the latter downwardly for release of contact lever 2.

The above described switch mechanism may be connected as shown in Fig. 7 to effect starting and stopping of an electric motor M. As is apparent from the foregoing, upon depression of push button I5 contact levers I and 2 are moved with a snap action from the positions shown in Fig. 2 to the positions shown in Fig. 3 to thereby move bridging contact 9 into engagement with its cooperating stationary contacts IlJ"---II) and bridging contact 1 out of engagement with its cooperating stationary contacts 8 4. With the circuit connections shown in Fig. 7 motor M is then connected across a source of current in-- dicated by lines L L in series with a starting resistance element R and a magnet 30 which will be hereinafter more fully described. Upon release of push button I5 contact lever 2 tends to return to the position shown in Fig. 2 to disconnect the motor from the supply circuit but the same is held in the position shown in Fig. 3 by its associated latch 20 which is adapted to be tripped as hereinbefore set forth upon depression of push button 21. Also upon release of push button I5 contact lever I tends to return immediately to the position shown in Fig. 2, in which position bridging contact 1 engages its cooperating stationary contacts li -8 to exclude the starting resistance element R and magnet 30 from the motor circuit. However, magnet 30 serves to hold contact lever I in the position shown in Fig. 3 until the current in the motor circuit drops to a value such as to prevent an excessive current rush upon exclusion of resistance element R.

Magnet 30 is mounted upon an insulating plate 3i which also carries the aforedescribed switch mechanism and resistance element R. Said magnet has an energizing winding 32 which is mounted upon a cylindrical core member 33 and said core member is secured to plate 3| by a screw 34 which passes through said plate from the rear thereof into a centrally located tapped opening in the rear end of said core member. The outer end of core member 33 projects beyond winding 32 and is slotted at 35 to provide a pair of pole projections 36 and 31 for attracting a projecting armature member 38 fixed to the free end of contact lever I. The pole projection 35 is surrounded by a plurality of D-shaped shading coils 39 which are secured to said projection by turned over portions 40 on the end of the latter. These shading coils are adapted to act in a well known manner to prevent chattering of the armature member 38 upon core member 33 by producing magnetic fluxes of different phase in the pole projections 36 and 31.

As hereinbefore set forth, magnet 30 serves to prevent return of contact element I to normal position until the current in the motor circuit drops to a value such as to prevent an excessive current rush in the motor circuit upon exclusion of the starting resistance element R. In practice it is desirable to provide for adjustment of the current value at which magnet 30 is adapted to release contact element I, and for this purpose said magnet and its cooperating armature 38 are so designed that by loosening screw 34 the magnet may be rotated with respect to the armature member. The width of the armature member 38 is less than the diameter of the core member 33 and by rotating the magnet with respect to the armature member the area of the face on pole projection 31 which is overlapped by the armature member 38 can be varied as shown in Figs. 5 and 6. As is apparent, the reluctance of the magnetic circuit between pole projection 31 and armature member 38 can thus be adjusted to vary the current value at which magnet 30 is adapted to release its cooperating armature member 38. Also as is apparent, rotative adjustment of the magnet about its axis varies the distance of the pole faces of pole projections 31 and 38 from the pivot of contact element I to also effect variation of the current value at which said armature is released.

In manufacturing the aforedescribed switch mechanism the angular position of the armature member 38 with respect to the core member 33 is likely to vary, as indicated by full and dotted lines in Fig. 4. This tends to vary the holding effect of the magnet 33 upon the armature member. However, in practice it has been found that by maintaining an air gap between pole projection 31 and the armature member 38 variations in the angular position of armature member 38 with respect to core member 33 will produce only a negligible variation in the holding effect of the magnet upon the armature member. As shown in Fig. 4 in order to maintain an air gap between pole projection 31 and the armaturemember 38, pole projection 35 projects beyond the former pole projection and serves as an abutment for said armature member.

The aforedescribed switch mechanism is preferably mounted within a box shaped enclosing casing II which is provided with a cover 42 having openings therein for receiving the push buttons I5 and 21. Also if desired the latch 28 may be provided with overload tripping means of the y.

character disclosed in the copending application of Clarence W. Kuhn, Serial No. 460,461, filed June 11, 1930. The tripping means disclosed in this application is of the electrothermal type and is adapted to respond upon overloads in the motor circuit to trip latch 20 for stopping of the motor and is also adapted to be reset by the switch operating mechanism.

What we claim as new and desire to secure by Letters Patent is:

1. The combination with a control device including a movable control part, of a holding winding therefor to be supplied with alternating current, a core member for said winding having a shading coil associated therewith to provide magnetic fields of different phase for attracting said control part to hold the same in a given position, and supporting means for said core member ,permitting rotary adjustment thereof about its axis for variation of the holding effect of said magnetic fields upon said control part.

2. The combination with a control device, including a movable control part biased towards a given position, said part having an armature member associated therewith, of an alternating current electromagnet for attracting said armature member to hold said control part in another position, said magnet having means associated therewith to provide magnetic fields of different phase for attracting said armature member, and a support for said magnet permitting adjustment thereof with respect to said armature member to provide for variation of the reluctance of one of said magnetic fields without substantial variation of the reluctance in the other of said magnetic fields.

3. The combination with a control device including a movable control member having an armature member associated therewith, of a holding winding therefor to be supplied with alternating current, a core member for said winding divided to provide a plurality of pole faces to coact with an overlapping pole face on said armature member, a shading coil associated with said core member and surrounding one of the divisions thereof, and supporting means for said members permitting relative adjustment of said armature and core members to vary the overlap of said armature member with respect to certain of the pole faces on said core member for variation of the holding effect of said winding.

4. The combination with a control device including a movable control part having an armature member associated therewith, of a holding winding therefor to be supplied with alternating current, a core for said winding divided to provide a pair of pole projections having pole faces to cooperate with an overlapping pole face on said armature member, one of said pole projections being adapted to abut said armature member and to maintain an air gap between said armature member and the other of said pole projections, a shading coil \surrounding said former pole projection, and supporting means for said core permitting adjustment thereof with respect to said armature member to vary the overlap of said armature member with respect to the pole face' of said last mentioned pole projection.

5. The combination with a control device including a movable control element having means associated therewith for biasing the same towards a given normal position, of a winding to be supplied with alternating current, and means associated with said winding to provide fluxes differing in phase for attracting said control element to hold the same in another position, said means being adjustable with respect to said control element to vary the attractive efiect of one of said fluxes upon said control element without substantial variation in the attractive effect of the other of said fluxes upon said control element.-

CLARENCE WILBUR KUHN. CLYDE F. ROBBINS. 

